'Insulated' (or 'insulfrog) frog points [ the 'frog ' is the vee-shaped bit where one running rail dissects the other) have a plastic 'frog'....the metal, or contact rails being sufficiently far apart from the vee as to not create a short circuit when a loco wheel passes through the frog area.
The advantage with this system is that the point itself can be an electrical 'switch'....thus, if used to form a siding, each 'arm' of the point will be isolated electrically if the point blades are set 'against' that track.
Thus one could 'drive' a loco through the point onto the siding, set the point the other way, leaving the loco isolated electrically.
One major disadvantage to this type of point construction, is the 'presence' of the 'dead' portion of the frog.....a loco of short wheelbase, or limited pickup via its wheels, may well 'stall' if driven slowly through the point.....the 'gap' in the frog, necessary to allow the wheel flanges to pass, also creates a 'dip' into which the wheel descends, lifting the opposite side wheels just clear of the rail, hence the 'stall?'
@Electrofrog' points, have an 'all-metal' frog...which, as your electrical knowledge tells you, might lead to a permanent short circuit unless something is done to isolate the frog area.
Thus, the frog area is isolated by 'cuts' from the surrounding rails, and the correct polarity electricity is provided by wiring from the surrounding point rails, usually via a fancy switch...thus, whichever way the point is set, the correct polarity is supplied to the frog .
Separate power supplies may even be necessary to the tracks beyond the point.......
The primary advantage of the electrofrog principle is that locos have CONTINUOUS electrical supply through the point.....therefore are less likely to stall at low speeds.
sit down with a bit of paper, draw out the rails of a point, add +ve and -ve to opposite rails, and follow the pattern through the point....you'll see what I mean.
Peco points are 'self-locking' ie technically need no levers if manually operated...( they have an over-centre spring).
Not sure about Hornby's points.
However, a tortoise motor might need a linkage with a bit of complication (omega loop, anyone?).....but I think it will be a favorite method of control.
